1. Technical Field
The present invention relates generally to automobile transmissions and more specifically to a method for assembling and testing for proper tolerances during assembly of the clutch.
2. Description of Related Art
An automatic transmission in an automobile utilizes a series of elements to control the smooth shifting from one gear to another. The clutch assembly is the main component that transfers hydraulic pressure to the rotational drive. Oil pressure is generated by an oil pump and directed by a valve body to the clutch.
The clutch comprises a set of steel plates, held by slots in a clutch drum, and a set of friction plates held in slots of a hub. The plates have clearance and can be rotated independently of each other. A piston sits in the base of the clutch. When a gear is required, oil is pumped under the piston, which compresses the plates and causes drive to be transferred through the compressed plates. The piston travel has to be a measured distance to ensure that the transfer of drive is correctly timed with the car""s gearshift. The clutch pack must also have enough clearance so that no drive is transferred when the clutch is xe2x80x9coffxe2x80x9d and full drive is transferred when the clutch is xe2x80x9conxe2x80x9d.
Partial drag or slipping of the plate sets will result in burning and ultimately failure of the transmission. These two critical points are controlled by the correct selection of a reaction plate on top of the clutch pack. This plate is available in different thicknesses so that the clearance within the clutch can be adjusted to correct tolerances, depending on the needs of the vehicle and transmission.
Therefore, it would be desirable to have a method for determining the proper clearance specification and ideal reaction plate thickness within the clutch during assembly of the transmission.
The present invention provides a method and apparatus for testing automobile transmission clutches. An operator assembles the clutch with the components on a fixture. The clutch then requires an internal spring assembly to be compressed and a circlip (retaining ring) to be installed to hold the spring under tension. The circlip is installed into a tool that is placed onto the clutch assembly. A press is then operated to push the circlip down over a cone in the installation tool, snapping the circlip closed in its final position. The press is then released and the tool removed.
A different tool is then placed onto the clutch assembly. This is a ring that will hold the clutch pack (steel and friction plates) together. The press is again operated and the cylinder compresses the clutch pack. The operator then sets a linear gauge to zero. By applying air pressure (calibrated to suit clutch pack application, approximating operating oil pressure when in the vehicle) to the clutch assembly through the lower fixture, the clutch pack is forced upwards to its closed position. The distance traveled by the clutch pack is visible on the linear gauge. This distance is the Clutch Clearance, which is critical to the operation of the transmission. If the clearance is out of range, the operator can remove the top reaction plate from the clutch pack and replace it with a thicker or thinner plate to achieve the correct tolerance.